This invention relates to tufting machines and more particularly to hooks for tufting machines for producing cut pile fabric having very low pile heights.
In Bardsley U.S. Pat. No. 4,303,025, assigned to the assignee of the present invention, apparatus is disclosed for moving the needle plate fingers of a tufting machine away from the needle path after the needles have penetrated the backing material as the hooks move toward the needle path. This allows a path of movement for the hooks which lies closely adjacent to the opposing face of the backing material. Thus, the limitations imposed by the needle plate finger geometry, i.e. the thickness of the needle plate fingers, on the pile height produced is removed so that low level cut pile may be formed. Accordingly, the distance of the cutting edge or underside of the bill of the hook from the backing material, and hence the dimensions of the tuft to be formed, can be determined by reference only to the geometry of the bill and the disposition and movement of the hook. When the needle plate fingers have moved away from the needle path, which is after the fingers have fulfilled their intended function of supporting the backing material during penetration, the backing material is supported on the upper surface of the hooks. Thus, the dimension of the tuft formed is determined by the geometry of the bill and the disposition and movement of the hook.
Such apparatus has been extremely successful and pile heights as low as 0.075 inch have been obtained, such low cut pile being unobtainable prior to the introduction of the apparatus of the aforesaid patent. The availability of producing such low level cut pile on tufting machines has virtually created a totally new market for tufting, that being the manufacture of cut pile upholstery fabrics. Such fabrics have heretofore been produced exclusively by weaving looms and knitting machines, but since the tufting process is faster and utilizes less yarn, its advantages are readily apparent. Since the greatest cost involved in the manufacture of tufted fabrics is the cost of the yarn, it is highly desirable to reduce the amount of yarn placed into the backing material, such reduction being attained by reducing the pile height. Consequently, it is apparent that a reduction in the pile height below that attained by the prior art apparatus is a significant achievement.
Since such low level pile is produced on very fine gauge machines, i.e. where the spacing between gauge parts is in the order of 1/16 to 1/20 inch, the thickness of the hooks is such that the hooks have relatively little strength. Narrowing the bill would merely reduce the strength even further.